3 Radioisotopic Methods for the Study of Nutrition
in Aquatic Animals
3.1 Introduction. Alternative Methods
The nutntIOn of aquatic animals governs the flow of material and energy
within and between aquatic biological communities; it is also the main factor
controlling their diversity in water basins. The study of nutrition is therefore
one of the most important in aquatic ecology. Research in this field aims to
describe the characteristics of the most common trophospecies of aquatic
animals in pelagic and benthic communities.
Among these characteristics are:
1. Spectrum of feeding (composition of food, food preferences).
2. Rate of feeding, with preferable kinds of food (food rations).
3. Assimilability of the ingested food and rate of assimilation.
4. Dependence of feeding rate on the concentration of food.
5. Threshold food concentration at which animals cover only their respiratory
losses.
6. Balance of expenditures of consumed food.
7. Metabolic losses.
Knowledge of these characteristics opens the possibilities of:
1. Establishing the place of a given group or community of hydrobionts in the
food web;
2. Evaluating their functional capability.
3. Establishing their actual functional activity in the water body in situ.
Comparison of experimentally established optimal and threshold food concentrations with the natural concentration in situ enables evaluation of food
supplies for a given trophical group under various seasonal and locational
environmental conditions.
The above information should be obtained experimentally for each important trophical group representing an energetically significant component
of a given ecosystem. I call it the trophic certificate of a given common (or key)
species, be it ciliate or fish (Sorokin and Giovanardi 1995). Only by having
such a trophic certificate for all basic trophic groups is it possible to derive
practically applicable mathematical models of aquatic ecosystems and energy
schemes. Otherwise, as often happens, modeling attempts are comparatively
useless, the final results being predicted by selected primary assumptions and
not based on an experimental background.
in Aquatic Animals
3.1 Introduction. Alternative Methods
The nutntIOn of aquatic animals governs the flow of material and energy
within and between aquatic biological communities; it is also the main factor
controlling their diversity in water basins. The study of nutrition is therefore
one of the most important in aquatic ecology. Research in this field aims to
describe the characteristics of the most common trophospecies of aquatic
animals in pelagic and benthic communities.
Among these characteristics are:
1. Spectrum of feeding (composition of food, food preferences).
2. Rate of feeding, with preferable kinds of food (food rations).
3. Assimilability of the ingested food and rate of assimilation.
4. Dependence of feeding rate on the concentration of food.
5. Threshold food concentration at which animals cover only their respiratory
losses.
6. Balance of expenditures of consumed food.
7. Metabolic losses.
Knowledge of these characteristics opens the possibilities of:
1. Establishing the place of a given group or community of hydrobionts in the
food web;
2. Evaluating their functional capability.
3. Establishing their actual functional activity in the water body in situ.
Comparison of experimentally established optimal and threshold food concentrations with the natural concentration in situ enables evaluation of food
supplies for a given trophical group under various seasonal and locational
environmental conditions.
The above information should be obtained experimentally for each important trophical group representing an energetically significant component
of a given ecosystem. I call it the trophic certificate of a given common (or key)
species, be it ciliate or fish (Sorokin and Giovanardi 1995). Only by having
such a trophic certificate for all basic trophic groups is it possible to derive
practically applicable mathematical models of aquatic ecosystems and energy
schemes. Otherwise, as often happens, modeling attempts are comparatively
useless, the final results being predicted by selected primary assumptions and
not based on an experimental background.